Each month brings new discovery and structural characterization of the proteins responsible for biological energy conversion and chemical transformation and regulation. Our proposal aims to better understand the fundamentals of the molecular mechanisms of biological oxidation and reduction that are basic to the operation of these proteins, and to uncover the natural engineering and architecture of oxidoreductases that support these processes. Such understanding should provide practical blueprints for recognizing the normal operating ranges of oxidative and reductive function, the tolerances to the challenge of stress, and the thresholds of failure and pathogenesis, as well as suggesting possibilities for remediation. Computational and experimental analysis of natural oxidation-reduction enzymes with molecular structures and identified function, are used to develop mechanistic insights and engineering guidelines that can be applied to oxidoreductases in general. Then de novo redox proteins are designed to uncover the essential structural aspects of protein architecture that accommodate this engineering. These minimal model proteins, maquettes, prove to be novel vehicles that reveal the essential structure-function relationships of tunneling and coupled reactions that are often obscured in highly complex natural proteins. Maquettes will be designed and synthesized to incorporate the chains of redox cofactors commonly used in natural oxidoreductases to lead electrons to and from enzymatic sites of substrate oxidation-reduction. Maquettes will be developed that bind substrates near redox cofactors to perform simple multi-electron catalysis. We focus principally on heme, flavin and redox-active amino acids such as tryptophan, tyrosine and cysteine as representative active elements of tunneling chains and a wide range of catalytic site actions and chemistries. Flavin as a two electron cofactor/substrate is used to investigate the mechanisms of the more complex redox reactions found in the catalysis of stable substrates. Nmr and x-ray diffraction reveal the structural foundations that give rise to the functions incorporated in these simple proteins. Electron transfer and multi-electron catalytic reactions will be activated by light and electric methods and analyzed by spectrophotometric and electrometric methods in solution and as structured monolayer films on electrode surfaces to dissect the thermodynamic and kinetics steps of electron and proton transfer. Maquettes, stable and adaptable by design, lend themselves to the development of biosensors and other molecular devices.